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Abstract:

An infinitely variable transmission comprising a pair of rotary, generally
conical, torque-transmitting members, each being mounted for rotation on
its geometric axis, the angularity of the axes, one with respect to the
other, being variable, the outer surfaces of each member having
torque-transmitting needles extending outwardly from the generally
conical surface, the needles of one member meshing with the needles of
its companion member, the needles being capable of flexing whereby torque
may be transmitted through the rotary members without frictional sliding
motion at the area of meshing engagement of the needles, the angularity
of one member with respect to the other permitting a wide
torque-transmitting ratio range.

Claims:

1. An infinitely variable power transmission mechanism for transmitting
torque from a rotary torque input shaft to a rotary torque output shaft
comprising first and second rotary members forming a torque flow path
from the torque input shaft to the torque output shaft;the torque input
shaft and the torque output shaft having axes that are spaced apart, one
with respect to the other;at least one of the first and second rotary
members having a generally conical surface, said surface having a
continuously curved profile that extends from one axial end thereof to
the opposite axial end;the rotary members having surfaces that are
engageable at an area of engagement;the first member and the second
member each including a cluster of torque transmitting needles on its
surface, the needles extending in a radially outward direction relative
to the shaft axes;the needles of the first member being in meshing
contact with the needles of the second member in the area of engagement
whereby torque is transferred from one rotary member to the other;the
rotary members being defined in part by ribbons having spaced pockets
formed thereon, a needle received in each pocket and held in place by
welding to define a ribbon and needle assembly; andthe ribbon and needle
assembly of the at least one rotary member being wound about the
generally conical surface of the at least one rotary member with one edge
of the ribbon of the at least one rotary member engaging the generally
conical surface of the at least one rotary member, the ribbon of the at
least one rotary member being generally perpendicular to the conical
surface, the one edge of the ribbon being secured to the conical surface.

2. The infinitely variable power transmission mechanism set forth in claim
1 wherein the needles are retained in the ribbon pockets by laser welds
and wherein the ribbon edge is secured to the conical surface by laser
welds.

3. The infinitely variable power transmission mechanism set forth in claim
1 wherein the needle tips are curved to facilitate engagement of the
needles at an area of mesh.

4. The infinitely variable power transmission mechanism set forth in claim
2 wherein the needle tips are curved to facilitate engagement of the
needles at an area of mesh.

5. The infinitely variable power transmission mechanism set forth in claim
1 wherein the one edge of the ribbon is secured to the conical surface by
welds.

6. The infinitely variable power transmission mechanism set forth in claim
5 wherein the needles are held in place in the pockets by welds.

7. The infinitely variable power transmission mechanism set forth in claim
5 wherein the welds are tack welds.

8. The infinitely variable power transmission mechanism set forth in claim
6 wherein the welds are tack welds.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application is a division of U.S. application Ser. No.
11/024,581, filed Dec. 29, 2004, which is a division of U.S. application
Ser. No. 10/129,215, filed May 23, 2002, now U.S. Pat. No. 6,964,630
dated Nov. 15, 2005, which is the U.S. national phase of PCT application
number PCT/US00/41398, filed Oct. 20, 2000, which further claims priority
to U.S. patent application Ser. No. 09/431,512, filed Nov. 1, 1999, now
U.S. Pat. No. 6,338,692 dated Jan. 15, 2002.

TECHNICAL FIELD

[0002]The invention relates to an infinitely variable power transmission
mechanism for use in transmitting torque from a torque input element to a
torque output element with a wide torque ratio range.

BACKGROUND ART

[0003]Infinitely variable torque ratio characteristics for a power
transmission can be achieved by using a friction belt and pulley
arrangement in which a drive pulley and a driven pulley, connected by an
endless belt, are adapted for torque transfer with an infinitely variable
torque ratio range by adjusting the pitch diameter of the pulleys, the
pitch diameter of the driving pulley increasing as the pitch diameter of
the driven pulley decreases, and vice versa. Examples of belt drives of
this kind may be seen by referring to U.S. Pat. Nos. 5,417,621 and
5,514,047.

[0004]It is known design practice also to provide infinitely variable
torque ratio characteristics by using a hydraulic pump as a driving
member and a hydraulic motor as a driven member. The pump and motor are
located in a closed hydrostatic fluid pressure circuit. By varying the
displacement of the pump, the effective speed ratio of the hydrostatic
transmission can be changed through a wide torque ratio range.

[0005]Various types of infinitely variable friction drives also are well
known. It is known design practice, for example, to use friction cone
members wherein the relative positions of the friction cones are
adjustable to provide an infinitely variable torque ratio characteristic.
An example of a friction cone drive mechanism may be seen by referring to
U.S. Pat. No. 5,681,235.

[0006]If an infinitely variable transmission is used with an internal
combustion engine to deliver torque to driven members, such as vehicle
traction wheels, the infinitely variable transmission characteristics can
be matched with the engine speed/torque characteristics such that the
engine may be operated with an engine throttle setting that will
correspond to a speed consistent with minimum brake specific fuel
consumption as variable torques are commanded by the operator. In this
way, the continuously variable transmission improves the overall
driveline efficiency.

SUMMARY OF THE INVENTION

[0007]The invention is an infinitely variable drive that comprises a
rotary, generally conical driving member and a rotary, generally conical
driven member. The driving and driven members are mounted for rotation,
respectively, on a torque input shaft axis and a torque output shaft
axis. Each carries needles on its surface. The needles mesh, thereby
permitting torque transfer between the driving and driven members.

[0008]Although the invention may be used in a driveline with an internal
combustion engine, it may be used also in other design applications:
e.g., accessory drives, window regulators, machine tool drives, etc.

[0009]The infinitely variable drive of the invention transmits torque from
a rotary torque input shaft to a rotary torque output shaft through the
rotary driving and driven members. The shafts have axes that are spaced,
one with respect to the other. Each member has a generally conical
surface, each surface having a continuously curved profile that extends
from one axial end thereof to the other. The driving and driven members
rotate on their respective shaft axes. Each member has a cluster of
torque transmitting needles on its surface. The needles of the driving
member mesh with the needles of the driven member in an area of mesh as
torque is transmitted between the members.

[0010]The surfaces of the rotary members of the invention are curved,
rather than precisely of conical shape, and are defined as surfaces of
revolution. The surfaces are in engagement, one with respect to the
other, so that torque is transmitted between the rotary members. The
angle of the axis of revolution of one member relative to the axis of
revolution of the other member can be changed so that the position of the
area of mesh of the needles on the surface of one member and the needles
of the other member will change.

[0011]The rotary members will be referred to, for purposes of this
description, as cone members. It should be understood, however, that
their surfaces of revolution are not precisely conical. Further, the
profile of each rotary member is curved, but the rotary members are not
necessarily hemispherical. Incremental areas of the surfaces of
revolution at various locations along the axis of rotation may have
differing radii of curvature.

[0012]Unlike conventional conical drive mechanisms of the kind shown, for
example, in the previously mentioned '235 patent, the area of mesh
between the driving and driven members of the invention is not
characterized by incremental portions of the area of contact of the
driving and driven members that have differential speeds. This is due to
the fact that the area of mesh is not characterized by frictional contact
between the surfaces of the driving and driven members. The area of mesh
is characterized instead by intermeshing needle elements densely formed
on the surfaces of each of the rotating members. The needles themselves
are in frictional engagement at the area of mesh as torque is distributed
from one cone member to the other. Differential movement of incremental
portions of the area of mesh for the respective rotating members is
accommodated by flexure of the intermeshing needles. This flexure of the
needles will permit continuous, efficient torque transfer between the
members throughout the entire ratio range of the transmission. The
flexure is coincident with frictional sliding motion of the needles of
one cone member relative to the needles of the other cone member.

[0013]Known friction cone drives typically have frictional contact between
the surfaces of friction cones. In actual practice, the cones do not
engage at a single point. Rather, a so-called contact patch is
established between the cones. Friction torque at the contact patch is
developed by a tangential force component on the surface of each cone
member. Because of the geometry of the conical surfaces, the contact
patch has incremental areas where sliding motion will occur between the
conical surfaces of the driving and driven members within the contact
patch. This sliding motion requires the presence of a hydraulic
lubricating oil film to avoid galling and deterioration of the friction
surfaces of the conical members. The presence of an oil film, however, is
imperfect protection against deterioration and wear of the friction
surfaces, especially when the transmission is operated in a high torque
range. The torque transfer between the driving and driven members of the
present invention, unlike torque transfer in such conventional friction
cone drives, takes place without the presence of a contact patch between
the members. The flexure of the intermeshed needles of applicant's
invention accommodate differential tangential velocities of the
incremental portions of the contact areas of the members when the needles
are in meshing engagement.

[0014]U.S. Pat. No. 4,028,949 discloses a linear transmission wherein
motion of a driving strip can be transmitted to a driven strip with a
ratio of unity. The motion transfer occurs through an endless belt
carrying bristles that mesh with bristles on the linearly movable strips.
It is not possible in an arrangement of this type to provide for
infinitely variable ratio characteristics.

[0015]The transmission of the invention makes provision for adjusting the
angularity of the rotating axis of each member in a continuous and smooth
fashion without the requirement for high adjustment forces. The
angularity of the conical members can be changed during torque transfer
so that the overall torque ratio can be varied without interrupting the
operation of the transmission.

[0016]The invention is capable of developing a wide range of ratios with
elements that are assembled with an economy of space. In one embodiment
of the invention, a ratio range of 10:1 to 0.4:1 has been successfully
demonstrated. A torque capacity of 200 lb.-ft. or more easily can be
accommodated using elements with a gross weight of 50 lbs. or less. It is
emphasized, however, that these features are representative of only one
embodiment of the invention. The torque capacity, for example, may be
greater or less, depending on the design requirements.

[0017]The needles may be manufactured using a cold-heading method. The
base of each needle may be enlarged to provide an anchor as the needles
are punched through the surface of the conical surfaces.

[0018]An alternative manufacturing method involves forming the needles
using a wire woven into a mesh matrix, the wires extending outward from
the matrix. The wires are bent in a reentrant fashion to define the
needles. The matrix is secured to the surfaces of the conical members.

[0019]Still another manufacturing method involves forming the needles
using wire stock. Wire segments are welded to pockets in a metal ribbon.
The metal ribbon is preformed with pockets on each side. The wire may be
cut as part of the welding step to form the needles as the wire is fed
into the ribbon pockets. The welded ribbon and needle assembly then is
wound about the surfaces of the conical members and held in place in a
subsequent welding step.

BRIEF DESCRIPTION OF DRAWINGS

[0020]FIG. 1 is an end view of the transmission mechanism;

[0021]FIG. 2 is a plan view of the transmission mechanism;

[0022]FIG. 3 is a view of the underside of a top plate seen in the plan
view of FIG. 2;

[0023]FIG. 4 is a top view of the transmission with the top plate removed,
the conical members and the carriers for mounting the conical members
being shown in phantom;

[0024]FIGS. 5a-5c are schematic representations of the torque-transmitting
driving and driven members including a pin and groove interface between
carriers for the driving and driven members and the transmission housing
for controlling the angular position of the torque-transmitting members;

[0025]FIG. 6 is a top view of the driving and driven members showing the
engagement interface where torque transfer occurs;

[0026]FIG. 7 is a cross-sectional view of the interface as seen from the
plane of section line 7-7 of FIG. 6;

[0027]FIG. 7a is an enlarged detailed side view of one of the
torque-transmitting needles carried by the surfaces of the drums seen in
FIG. 6;

[0028]FIG. 7b is a view showing the ends of the needles carried by the
drums of FIG. 6 as seen from the plane of section line 7b-7b of FIG. 7;

[0029]FIGS. 7c and 7d show alternate needle shapes that can be used
instead of the needle shape shown in FIG. 7a;

[0030]FIG. 8 is a perspective view of the surfaces of the driving and
driven members shown in FIG. 6 and the area of mesh of the needles
carried on the surfaces;

[0031]FIG. 9 is a partial cross-sectional view of one construction of a
needle that may be pushed through the surfaces of the conical driving and
driven members as seen from the plane of section line 9-9 of FIG. 8;

[0032]FIG. 9a is an end view of the needle of FIG. 9 as seen from the
plane of section line 9a-9a of FIG. 9;

[0033]FIG. 10 is a partial assembly view of a construction that comprises
a mesh wire matrix with needles in the form of a continuous wire woven
into the matrix;

[0034]FIG. 11 is another partial assembly view of a construction that
comprises a ribbon with undulations that define pockets within which wire
segments are welded, the wire segments forming needles; and

[0035]FIG. 11a is an end view of the partial assembly of FIG. 11.

PARTICULAR DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0036]The transmission assembly of the invention is generally designated
by reference character 10 in FIGS. 1 and 2. It includes a main case or
housing having a base 12 and a top plate 14. A pair of side plates 16 and
18 supports the top plate 14.

[0037]For purposes of this description, the housing is shown as an open
housing to allow for a better view of the cone members. In actual
practice, the housing preferably would be closed. This would facilitate
the use of a lubricant, such as powdered graphite, powdered polymers or
liquid hydrocarbon lubricant. The cone members, furthermore, would be
protected by a closed housing when the invention is used in a harsh
environment.

[0038]A pair of rotary, generally conical members is seen in the side view
of FIG. 1 at 20 and 22. A torque output shaft, schematically shown in
FIG. 1 at 24, is connected drivably to cone member 20. Each cone member
is journalled on a separate carrier for rotation about its geometric
axis. The carrier for cone member 20 is shown at 24, and the carrier for
cone member 22 is shown at 26. The carrier 24 comprises an upper plate 28
and a lower plate 30. Side members 32 and 34, together with the members
28 and 30, define a carrier housing for the cone member 20.

[0039]The cone member 20 is mounted for rotation about its geometric axis
within the carrier 24. A torque input shaft 36 coincides with the
geometric axis of the cone member 20 and is connected directly to it.
Shaft 36, as seen in FIG. 4, may be connected to a drive shaft 37 by a
universal joint; preferably, a constant velocity universal joint. Shaft
36 extends through openings formed in the side members 32 and 34.

[0040]Carrier 26 comprises an upper plate 38 and a lower plate 40. Side
members, one of which is shown at 42, together with the upper plate 38
and the lower plate 40, define an enclosure for the cone member 22. The
cone member 22 is mounted for rotation about its geometric axis in the
carrier 26. A torque output shaft 44 is journalled in openings formed in
the side member 42 and in a companion side member 46, as seen in FIG. 4.
The torque output shaft 44 coincides with the axis of the cone member 22
and is connected directly to it.

[0041]The shafts 36 and 44 may be connected, respectively, to drive shaft
37 and to a driven shaft, not shown, by constant velocity universal joint
that accommodate axial sliding motion. This will permit the cone members
to adjust axially when cone members are of unequal size or are of
non-hemispherical profile. Shaft 37 is shown as a spline shaft wherein
the splines define a sliding spline portion of a constant velocity
universal joint.

[0042]The upper plate 14, as seen in FIG. 1, has a slot or channel of
rectangular cross-section, as shown at 48. From the perspective of FIG.
1, the slot 48 is on the underside of the plate 14. An adjustable slide
50 is situated in the slot 48. On each side of the slide 50 are
stabilizer rollers 52, as seen in FIGS. 1 and 3, which guide the slide 50
as it is moved within the slot 48 in the direction of the arrow 54 seen
in FIGS. 3 and 4. A pair of bearing strips 63 and 66 is located in the
rectangular groove 48.

[0043]The slide 50 has a pair of cylindrical guide members 56 and 58
situated in guide slots 60 and 62 in upper plates 28 and 38 for the
carriers 24 and 26, respectively. The groove 60 conforms generally to the
shape of the outer surface of the cone 20 and the groove 62 conforms
generally to the shape of the outer surface of the cone 22.

[0044]The upper surface of the lower plate 12 is provided with ball
bearings 64 for supporting the lower plates 30 and 40 of the carriers 24
and 26, respectively. The bearings 64 preferably are spherical bearing
elements seated in a semispherical pocket formed in the lower plate 12.
The spherical bearing elements, when adapted for universal movement in
the semispherical pockets, permit the lower plates 30 and 40 of the
carriers 24 and 26, respectively, to float on the lower plate 12.

[0045]When the slide 50 is moved in rectangular slot 48, the guide members
56 and 58 will cause the carriers 24 and 26 to change their angularity
relative to the direction of motion of the slide 50. The upper plate 28
has a curved surface 67, which contacts a companion curved surface 68
formed on plate 38. Adjustment of the slide 50 in one direction or the
other will cause the curved surfaces 67 and 68 to have rolling contact at
their point of tangency.

[0046]The curved surfaces 67 and 68 generally conform in shape to the
profile of the cone members 20 and 22, respectively. They may be changed,
however, if the design requirements make it desirable to vary the depth
of mesh of the needles at the area of mesh.

[0047]The upper plate 38 has grooves 70 and 72, which are engaged
respectively by guide pins 74 and 76 secured to the underside of the
upper plate 14. Similarly, the upper plate 28 of the carrier 24 has guide
grooves 78 and 80, which register with guide pins 83 and 85,
respectively. These guide pins 83 and 85 are secured to the undersurface
of the top plate 14. The grooves 78 and 80, together with the pins 83 and
85, respectively, determine the angular position of the carrier 24 as the
slide 50 is moved. Similarly, the guide grooves 70 and 72 in the upper
plate 38, together with the guide pins 74 and 76, control the angularity
of the carrier 26 as the slide 50 is adjusted in one direction or the
other.

[0048]As best seen in FIGS. 1 and 3, the underside of the top plate 14 is
provided with ball bearings 79. These bearings comprise a cylindrical
bearing element that is received in a semispherical pocket. They
essentially are of the same design as the bearings 64. The bearings 64
and the bearings 79 permit the carriers 24 and 26 to float within the
confinement of the housing defined by upper and lower plates 14 and 12
and the side plates 16 and 18.

[0049]Although a mechanical slide 50 is shown for purposes of this
description, it is emphasized that other types of actuators for adjusting
the cone members may be used. For example, servo actuators or a
screw-feed drive could be adapted to perform the function of slide 50.
Further, any of several known bearing arrangements may be used to obtain
the floating function of bearings 64 and 79 and the guiding function of
bearing strips 63 and 66.

[0050]In the particular embodiment illustrated in the drawings, the cone
member 20 is a driving member and the cone member 22 is a driven member.
The axis of rotation of the member 20 is shown at 82 in FIG. 4, and the
corresponding axis of rotation of the cone member 22 is shown at 84. The
effective diameter of the cone surface at the area of tangency for the
cone members is less in the case of cone member 20 than in the case of
cone member 22. When the cone members are positioned as shown in FIG. 4,
the torque output shaft 24 will be driven at a speed that is less than
the speed of rotation of the torque input shaft 36. The overall speed
ratio is changed as the carriers 24 are adjusted angularly. When the area
of mesh or tangency for the cone members is near the small diameter end
of the cone 20, the area of mesh or tangency for the cone member 22 is at
a maximum radius. When the carrier 24 is adjusted in the opposite
direction to its extreme position with the guide member 56 at the upper
end of the guide slot 60, the areas of mesh or tangency of the cone
members occur at a maximum radius for the cone 20 and at a minimum radius
for the cone 22.

[0051]FIGS. 5a, 5b and 5c show the cone members in their various angular
orientations. In the case of FIG. 5a, the carrier 24 and the carrier 26
are in their maximum underdrive positions. In the case of FIG. 5c, the
carriers 24 and 26 are in their maximum overdrive orientation. In the
case of FIG. 5b, the carriers 24 and 26 are positioned at an intermediate
speed ratio position.

[0052]The density of the needles on the cone members can be changed
depending upon the design requirements of a particular application.
Further, the size of the needles (i.e., the length and diameter) also can
be changed, as required. In one embodiment of the invention, the density
is about 14 thousand needles per square inch.

[0053]FIGS. 6 and 7 show the details of the cone members. FIG. 6 shows the
cone members with an angular orientation corresponding to a mid-range
speed ratio. The cone members are formed of a suitable rigid structural
material. The cone member 20 is fixed, as explained previously, to the
torque input shaft 36 and cone member 22 is fixed to the torque output
shaft 44. The curved surface of the cone member 20 has torque
transmitting needles 86 and the curved surface of cone member 22 has
corresponding needles 88. The needles 86 and 88 are secured in cantilever
fashion to the surfaces of the cone members and generally extend
perpendicularly from their respective curved surfaces. The needles 86
intermesh with the needles 88 so that as torque is applied to the cone
member 20, the cone member 22 is driven in synchronism. As the cone
members rotate, one with respect to the other, the needles 86 and 88 move
into and out of registry so that there is a continuous driving connection
between the cone members as torque is transmitted across the interface.
The interface is established by the intermeshed needles. Flexure of the
needles at the interface accommodates the varying angular velocities of
incremental segments on one cone curved surface with respect to the
corresponding incremental surface on the companion cone curved surface.
There is no physical contact between the curved surfaces as in the case
of a friction cone drive of conventional construction.

[0054]FIG. 8 is a perspective view of the generally conical surfaces of
the driving and driven members 20 and 22. The area of mesh for the
needles on the members 20 and 22 is indicated at 94. As indicated, the
area of mesh is generally elliptical. The location of the area of mesh on
the members 20 and 22 will shift between the ends of the members. The
direction of shift depends upon whether the torque ratio is increasing or
decreasing.

[0055]The members 20 and 22 are shown in phantom in FIG. 8 to clarify
their relative dispositions as the area of mesh 94 is generated.

[0056]FIG. 6 shows a plan view of the needles of the cone members. The
needles are arranged in a dense pattern over the surfaces of the cone
members. The spacing between adjacent needles may be about 0.0085 to
0.0090 inches in the direction of the axis of each cone members. The
spacing between adjacent needles measured in a direction transverse to
the axis of each cone members also is approximately 0.0085 to 0.0090
inches. The needles themselves are generally cylindrical, as indicated in
the detailed view of FIG. 7a. The diameter of the needles may be
approximately 0.004 inches so that only a slight clearance is provided
between the needles of one cone member relative to the needles of the
other cone member. A typical length for the needles may be 0.060 inches.

[0057]FIG. 7b is an enlarged plan view of a small area of the needles for
the cone members. The dimension "d," represents the spacing of the
needles in the direction of the axis of rotation of the cone members, and
the dimension "d2" represents the spacing of the needles in a
direction transverse to the axis of rotation. These dimensions may be
0.0085 to 0.0090, as mentioned above.

[0058]The ends of the needles may be bullet-shaped or rounded as seen in
FIG. 7a to facilitate movement of the needles of one cone member into
registry with the needles of the other cone member as the cone members
rotate. Other designs for the ends of the needles also are possible. For
example, the needles may have a sharp tip, as shown at 86' in FIG. 7c; or
a blunt tip, as shown at 86'' in FIG. 7d. It is possible as well to use
needles that are not of round cross section. Further, the cross sectional
area of the needles may be variable from the base to the tip.

[0059]The geometry of the surfaces of the cone members is a function of
the overall ratio range that is required for a particular application for
the transmission. In the embodiment shown in FIG. 6, the cone member 20
is of lesser diameter than the cone member 22.

[0060]When the carriers are angularly adjusted upon movement of the slide
50, either or both may shift in the direction of motion of the slide.
This shift is due to the fact that the cone members usually are of
unequal diameter for any given length. This shift is accommodated by the
guide grooves 70, 72, 78 and 80 as the carriers 24 and 26 float on the
bearings 64 and 78. The surfaces 67 and 68 on the carriers will
accommodate sliding engagement, one with respect to the other, as well as
rolling engagement.

[0061]The needles may be formed of high carbon alloy steel. Other
materials that may be used for this purpose are structural polymers or
spring steel. It is preferable to use powdered graphite as a lubricant
for the cone members to reduce friction, although lubricating oil or a
lubrication oil mist can be used, particularly if cooling is needed.
Polymer powder or a liquid polymer lube also may be used. But an oil film
at the interface for the cone members is not required for torque transfer
as in the case of prior art friction cone drives. All of the torque
transfer is accommodated by the needles as they flex without
over-stressing of the needles. The needles themselves act as cantilever
beams that are subject to a degree of flexure well below the elastic
limit.

[0062]The term "needles" is used herein to describe the area of mesh. For
purposes of this description, the term "needles" should be construed to
include fingers, protrusions, wires, pins, etc. For low torque
applications, non-metallic needles such as molded nylon needles or
various nonferrous, polymer-based materials could be used.

[0063]Although the needles for the disclosed embodiment of the invention
extend radially from the axes of rotation of the cone members, they may
be offset or biased in a non-perpendicular fashion if that configuration
would be required for a particular design.

[0064]FIG. 6 shows an annular area 90 on the small end of cone member 20
and a corresponding annular area 92 on the large end of cone member 22.
These areas lack needles (i.e., they are bald). When the cone members are
adjusted to their maximum underdrive positions with the areas 90 and 92
in substantial registry, the infinitely variable drive will be in a
neutral mode with no torque transfer between the cone members. The
surfaces 67 and 68 on the carriers can be designed to provide a slight
clearance between the surfaces 90 and 92 when they are in registry. This
neutral mode feature makes it possible to provide interruption in torque
transfer through the torque flow path without the need for a separate
neutral clutch.

[0065]The density of the needles for each cone member can be nonuniform if
that is required for a particular design application. Further, the
density of the needles of one cone need not be the same as the density of
the needles of the companion cone member. Again, this feature would be
determined by design requirements.

[0066]FIG. 9 shows a needle in the form of a pin 96, which may have a
length of approximately 0.160. A bullet taper portion 98 at one end of
the pin 96 is rounded to a point 100. The base of the pin shown at 102 is
enlarged relative to the thickness of the pin and is formed with a
generally square shape, as seen in FIG. 9a. The pins are received in
openings 22a in the surfaces of the cone members.

[0067]The pin 96 can be formed, for example, by a cold heading process
using stainless steel material. In some applications, it would be
possible to use nylon rather than stainless steel. The thickness of the
pin may be about 0.006 in.

[0068]The individual pins 96 can be pushed through a matrix at the drum
surfaces. The drum surface can be a separate matrix attached to the drum,
although the drum surface may be used as the retaining matrix.

[0069]An alternate needle design is shown in FIG. 10. The needles of FIG.
10 comprise loops 104, which may be made of the same material used in
forming pins 96. The loops extend through openings in a woven matrix 106.
The matrix 106 has wires or fibers 108 and 110 extending perpendicularly
one with respect to the other. The loops 104 engage the fibers or wires
110 and extend radially outward from the plane of the woven matrix. The
wires 104 extend in a reentrant fashion to define rounded points 112. The
wires 108 and 110 may be formed using the same material used in making
the needles.

[0070]A welding technique can be used to form the cone surface and pin
assembly shown in FIGS. 11 and 11a. In the embodiment of FIGS. 11 and
11a, steel wires 114 are fed into the pockets 116 of ribbon stock 118.
The wires 114, as well as the ribbon stock 118, can be stainless steel
(SAE 302-SS). A micro-welding technique can be used to attach the wires
114 to the pockets 116 using a laser tack weld step, as shown at 120. The
tack welds 120 may be located approximately one-third of the distance
between one edge 122 of the ribbon 118 and the other edge 124. The ribbon
is preformed using a crimping tool which forms pockets 116 before the
wires 114 are inserted. Although a tack weld is shown on each side of
each wire 114, a single weld may be used on only one side of the wire if
that is appropriate for a particular design. The ribbon stock is wound
about the cone members. One edge of the ribbon stock is welded to the
surface of the cone members using a welding technique such as tack
welding.

[0071]In one embodiment of the invention, the width of the ribbon may be
0.400 in. to 0.800 in. The thickness of the ribbon may be approximately
0.003 in. to 0.010 in. The wires 114 can be fed into the pockets of the
ribbon from a spool. When they are in place, the laser will cut the wires
114 to the desired length, which may be about 0.140 in. The bullet shape
of the pin that is formed from the wires 114 may be similar to that shown
in FIG. 9. The bullet curvature can be formed by the laser cutoff step.

[0072]After the welding step is completed, the pin and ribbon assembly is
wound on the cone surfaces. The cone surfaces may be steel, and the edge
122 can be welded with a continuous weld, such as a laser weld, to the
surfaces of the cones so that the pins formed from the wires 114 extend
generally perpendicularly with respect to the cone surface.

[0073]The weld at the junctures between the ribbon and the pins is seen at
120 in FIG. 11 on one side of the ribbon. A corresponding weld is formed
in the joint in the pockets on the opposite side of the ribbon, as
indicated in FIG. 11a.

[0074]The laser welding of the edges of the ribbon windings takes place as
the ribbons are wrapped around the steel cone surface.

[0075]A bond at the junctures of the pins and the ribbons may be made by
welding techniques other than laser welding. Brazing and soldering
techniques also may be used to form the bond, depending on the design
requirements. Such alternative bonding techniques may be used also to
secure the edge of the ribbons to the cone surfaces.

[0076]Each of the embodiments shown in FIGS. 9, 9a and 10, on the one
hand, and FIGS. 11 and 11a on the other hand, may involve securing the
pins directly to the drum surface. The woven matrix 108 shown in FIG. 10
may be a separate matrix, or it may define the drum surface itself.
Similarly, the edges 122 of the ribbons 118 of the embodiment of FIGS. 11
and 11a may be secured directly to the drum surface using a welding
technique, or they may be secured to a substrate. The substrate, in turn,
may be wrapped around the drum surface.

[0077]In the case of the embodiment of FIG. 10, the wire loops, which
define the needles, can be formed from the same material of which the
woven matrix 106 is formed. That material may be stainless steel, or
nylon, or other structural material depending on the design requirements.

[0078]Although embodiments of the invention has been disclosed, it will be
apparent to persons skilled in the art that modifications may be made
without departing from the scope of the invention. All such modifications
and equivalents thereof are intended to be covered by the following
claims.